Combustion chamber for internal combustion engines



1934- R. N. JANEWAY 1,971,913

COMBUSTION CHAMBER FOR INTERNAL COMBUSTION ENGINES Filed Jan. 2, 1931 2 Sheets-Sheet 1 NVENTOR.

1 HUBER T N. JANE WA X 1934- R. N. JANEWAY 1,971,913

COMBUSTION CHAMBER FOR INTERNAL COMBUSTION ENGINES Filed Jan. 2, 1931 2 Sheets-Sheet 2 VIII/III PERCENT OFMAXIMUM FLAME TRA VEL, INVENTOR- X A S W n 5 M N m M m Z/ 7/. Z MQM wy RB Patented Aug. 28, 1934 UNITED STATES PATENT OFFICE Robert N. Janeway, Detroit, Mich., assignor to Chrysler Corporation, Detroit, Mich., a corporation of Delaware Application January 2, 1931, Serial No. 50631 8 Claims.

This invention relates to an improved combustion chamber for internal combustion engines.

During operation of an internal combustion engine, repeated high pressures are developed by the combustions in the combustion chambers which subject the engine structure to shock loads. When these repeated shock loads are excessive, they increase the defi'ection of the load carrying members, particularly the crank shaft and crank case of the engine, to such an extent that unpleasant vibratory sensations of roughness are perceptible. The engine parts are subjected to serious abuse during aggravated conditions of this character which results in their untimely failure.

I have found that the intensity of the shock factors of the combustions which occur in an internal'combustion engine depend mainly upon the acceleration. in the rate of pressure rise during the combustions, the maximum rate of pressure rise being an additional factor. When the acceleration of the rate of pressure rise is comparatively low and uniform, smooth engine operations are obtainable.

The acceleration of the rate of pressure rise in a combustion chamber, with respect to time, is influenced by a number of factors, such as the area of the'flame front during combustion, the velocity of the travel of the flame front and the density of the mixture, at, or immediately in advance of the flame front. The initial velocity of the flame front travel can be controlled somewhat by properly predetermining the shape of the combustion chamber in the immediate vicinity of the ignition point or spark plug, but in the portion of the course of the flame front that is remote from the ignition point, the velocity of the flame front is practically uncontrollable and only the area of the flame front is controllable.

The main objects of this invention are to produce smoothness in the running conditions of an internal combustion engine; to control the acceleration in the rate of pressure change in a combustion chamber of an engine so as to maintain a substantially uniform, moderately low acceleration in the rate of pressure rise throughout the entire duration of each explosion; to provide a combustion chamber which predetermines the flame front area throughout its course of travel so as to maintain a substantially uniform rate of change in the rate of pressure rise from the start to the completion of each combustion; to provide a combustion chamber having varying contour and varying dimensions in both length, breadth and thickness which is adapted to suitably change the flame front area as it progresses throughout its course of travel in order to prevent the rate of pressure rise from increasing excessively at any stage of an explosion; and to provide for the proper placement of the ignition point or spark plug with respect to the course in which the flame front travels so as to give the desired variation in flame front area.

An illustrative embodiment of the invention is shown in the accompanying drawings, in which:

Fig. 1 is a fragmentary section of an internal combustion engine taken substantially horizontally through a combustion chamber thereof which embodies my invention.

Fig. 2 is a vertical section taken on the line 2-2 of Fig. 1.

Fig. 3 is a vertical section taken on the line 33 of Fig. 2.

Fig. 4 is a diagrammatic view, illustrating graphically, the percentage of total volume swept by the flame front with respect to the percent of maximum flame front travel.

In the form shown, my improved combustion chamber 1 is illustrated in conjunction with a cylinder head 2 and cylinder block 3 of an internal 3 combustion engine of conventional construction.

Although the combustion chamber varies in height at divers locations, it is generally of the flat type for its walls confine a combustion space that is spread out over a substantial area having a substantially greater length than breadth and the depth of the combustion space is less than its width at substantially all transverse cross sections of the main body portion of the chamber.

The cylinder block is provided with longitudinally spaced intake and exhaust ports 4 and 5, respectively, in which valves 6 are located. A compressible gasket 7 is provided between the cylinder head 2 and block 3 for forming a leak proof seal. The head 2 is cored out, as illustrated at 8 so as to form chambers for receiving a cooling medium.

Formed in the head 2 are top and side walls 9 and 10, respectively, which, together with the upper wall 11 of the cylinder block 3, form the boundaries of the main combustion chamber 1 exclusive of theclearance space 10 between the piston and the cylinder head. The contour of the side walls 10 of the combustion chamber 1 is best illustrated in Fig. 1, and the contour ofthe upper wall 9 is clearly shown in Fig. 2.- In the 1 the intake and exhaust ports 4 and 5, respectively,

and the narrowest breadth occurring over the cylinder 12 in which a conventional piston 13 is received. The maximum height of the combustion chamber-1 occurs at a location on the piston side of the middle of the length of the chamber as indicated at 14 in Fig. 2. The minimum height occurs at the valve end of the combustion chamber. The height of the chamber decreases continuously, without reversal, from both sides of the maximum height and the minimum height is at least one-half the maximum height.

Mounted on the cylinder head 2 is a spark plug 15 havinga spark gap 16 which is located between the longitudinal axis of symmetry of the chamber and the exhaust port, as indicated at 16 in Fig. l. The location of the spark gap with respect to the boundaries of the chamber is particularly important since during each combustion, the flame front travels from the spark gap outwardly in spherical formation. This location is best determined, during designing of any chamber, by trial and error. In locating the spark gap, it is also necessary to maintain the volume of the spherical section that produces the maximum flame front area within a limit of 50% of the entire volume of the combustion chamber.

When a spark gap location, which is satisfactory with respect to the valve positions and general design of the engine is selected, the maximum flame front area with respect to that location is determined with the aid of a plurality of concentric circles having their center at the selected spark location. The longest arc of these circles which is included within the boundaries of the chamber defines the location of the flame front of maximum area. The volume included within the maximum flame front area may be calculated in various ways. This is preferablydone, however, in the manner illustrated in the drawings. When the fragmentary spherical surface having the maximum area included between the boundaries of the chamber and which is generable about the point 16 is located, the volume of that part of the chamber included within the curvature of this fragmentary spherical surface may be conveniently calculated by any well known method of determining the volumes of irregular objects. Simpson's rule is preferably used for this purpose, however, any other approximately accurate method may be employed. In the illustrative development shown in Figs. 1 and 2, that portion of the are 17 representing the fragmentary spherical surface of maximum area, which is located between the longitudinal axis of symmetry 19 and the intersection 20 of the are 17 with the walls of the chamber, is bi-sected by the line 18 so as to locate the mean height of the fragmentary spherical surface. The intersection of the bi-sector 18 and are 17 is then projected down to Fig. 2 until it-intersects the inner surfaces of the top wall 9 of the combustion chamber. A horizontal line 21 is then drawn from the latterintersection to the are 17 appearing in Fig. 2, the distance from the floor 11 of the combustion chamber to the horizontal line 21 being the mean height of the section used in calculating the volume. Then the spherical section included within the are 17 is treated as a cylindrical section by erecting a vertical line 22 which intersects the arc 17 in such a manner as to pro- 'vide substantially equal areas 23 and 24 between equal to the distance from the point 16 to the line 22, may then be conveniently calculated by Simpsons rule.

The volume included by the flame front at successive positions may be determined in the above manner and the relation between the volume of the combustion chamber occupied by burned gas, and length of flame travel at any corresponding selected position of the flame front may be then determined.

It is found that the acceleration of the rate of pressure rise in a combustion chamber with respect to time falls within proper limits, when, in addition to the above specification, a chamber is provided in which is generable about the spark gap, a fragmentary spherical surface having a 90 maximum spherical area and occupying not more than 50% of the volume of the chamber, the total volume of the chamber including the volume of the clearance space when piston is at top dead center position.

The relation between the volume of the chamber occupied by burned gas and the occurrence of the maximum flame front area may be accurately determined in the manner illustrated in Fig. 4, wherein a curve 25 is plotted having ordinates in terms of percent of total volume swept by the flame and abscissas in terms of percent of the maximum distance of flame travel from the ignition point. The slope at any point on this curve may be found by determining the ratio of an increment of volume (dv) to an increment of length (d1) this ratio being equal to the instantaneous flame front area. Hence the maximum slope indicated by the line 26 also corresponds to the maximum flame front area. In the illustration shown, the maximum slope occurs before 50 of the total volume is swept by the flame.

In addition to these requirements the volume of the chamber should be so distributed that at the location of maximum flame front area, the ratio of an increment of volume (dv) with respect to an increment of length of flame travel (dl),'computed as units of percentage of volume divided by units of percentage of length, should not exceed 2.25. 120

The side walls, top and floor, which bound'the combustion chamber 1, are spaced with respect to each other so as to allow the flame front area to increase continuously without reversal up to its maximum area and to cause the flame front area to decrease continuously without reversal as it travels from the location of maximum area to the piston end of the chamber. This construction prevents the acceleration of the rate of pressure rise in the combustion chamber from becoming excessive and therefore prevents the occurrence of severe shock during combustion of the charge in the. chamber.

Although but one specific embodiment of this invention has herein been shown and described, it will be understood that various changes in the size, shape and arrangement of parts may be made without departing from the spirit of my invention and it is not my intention to limit its scope other than by the terms of the appended claims.

What I claim is: l I

1.- An internal combustion engine including a substantially flat type combustion chamber of irregular contour-having rigid walls and provided with a main body portion having a substantially 1 5 greater length than width and having a depth of less magnitude than its width atsubstantially all of its transverse cross sections, an ignition point serving said chamber, said point being so posi- ,tioned relative to the irregular chamber that the portion of a spherical surface of maximum area which can be generated in said chamber with said point as a center will, together with the intersected portions of the walls of said chamber adjacent said ignition point, encompass not more than 50% of the volume of the chamber and not less than 30% thereof.

2. An internal combustion engine having a cylinder bore and provided with a substantially flat type combustion chamber of irregular contour extending over a portion substantially less than all of said bore,'an ignition point disposed in said chamber adjacent one end thereof, said chamber increasing in height and decreasing in width throughout the intermediate portion of the length thereof extending from said ignition point towards the opposite end of the chamber.

3. In an internal combustion engine including a block having a cylinder and adjacent valves, a cylinder head on said block, a combustion chamber in said cylinder head registering at one end with portions of said cylinder and at its other end with said valves including a substantially fiat floor and a gable-like roof inclined from a minimum height at the valve end of said chamber to a maximum height at a point adjacent the cylinder end thereof and having side walls converging toward the cylinder end of said chamber from points substantially adjacent the common diametrical axis of said valves, substantially opposite the ignition point, and terminating in an end wall substantially perpendicular to said floor.

4. In an internal combustion engine including a block having a cylinder and adjacent valves, a cylinder head on said block, a combustion chamber in said cylinder head registering at one end with portions of said cylinder and at its other end with said valves including a floor and a gablelike roof having sections inclined in opposite directions from the longitudinally spaced ends of said chamber to a point adjacent the cylinder end thereof and having side walls converging toward the cylinder end of said chamber substantially from the intersecting points of the common center line of said valves and the side walls of said chamber adjacent said valves respectively and terminating in an end wall projecting upwardly from the floor of said chamber in angular relation to the inclined roofsection adjacent thereto.

5. In an internal combustion engine including a block having a cylinder and a cylinder head on said block and including adjacent valves, a combustion chamber in said cylinder head registering at one end with portions of said cylinder and at its other end with said valves including a floor and a gable-like roof inclined from a minimum height at the valve end portion of said chamber to a maximum height at a location adjacent the cylinder end thereof and having side walls converging toward the cylinder end of said chamber from points substantially adjacent the common diametrical axis of said valves substantially opposite the ignition point and terminating in an end wall projecting upwardly from the floor of said'chamber in angular relation to the portion of said roof adjacent thereto.

6. In an internal combustion engine including a block having a cylinder and adjacent valves, a cylinder head on said block, a combustion chamber in said cylinder head registering at one end with portions of said cylinder and at its other end with said valves including a floor, an ignition point serving said combustion chamber located at the valve end thereof and within the boundaries of a quadrilateral defined by parallel diameters of said valves extending longitudinally of said chamber and lines joining the corresponding ends of said diameters, said combustion chamber having a gable-like roof inclined from a minimum height at the valve end of said chamber to a maximum height at a point adjacent the cylinder end thereof and having side walls converging toward the cylinder end of said chamber substantially from the intersections of the common center line of said valves with said side walls, and terminating in an end wall projecting upwardly from the floor of said-chamber in angular relation to the portion of said roof section adjacent thereto. l

7. In an internal combustion engine including a block having a cylinder, a cylinder head on said block, a combustionchamber in said cylinder head registering at one end with said cylinder, a pair of valves located at the other end of said chamber, said chamber including a gable-like roof, inclined from a minimum height at its valve end portion to a maximum height at a location adjacent its cylinder end portion and having side walls converging toward the cylinder end of said chamber from points substantially adjacent the intersections of the common diametrical axis of said valves and said side walls and'terminating in an end wall.

8. In an internal combustion engine including a block having a cylinder, a combustion chamber in said engine registering at one end with said cylinder, and a pair of valves located at the other end of said chamber, said chamber including a roof having a pair of sloping sections each inclined in opposite directions to a maximum height at a location adjacent the cylinder end of said chamber and having side walls converging toward the cylinder end of said chamber from points substantially adjacent the intersections of the common diametrical axis of said valves and said side walls and terminating in an end wall.

- ROBERT N. JANEWAY. 

